Turkish police have urgently ramped up their presence in Istanbul, with special forces and military hardware deployed to the streets and orders to down aircraft without warning, following unconfirmed reports of rebel helicopters approaching the city. Meanwhile, F-16 fighter jets have been sent to patrol Turkish airspace.

Turkish media report 3 helicopters were spotted over Istanbul at 22:30 local time

A state of emergency has been imposed in Istanbul and 1,800 additional special police forces have been deployed, the state Anadolu Agency reported.

Armored vehicles have also been deployed to key locations in Istanbul, Sputnik news agency reported earlier.

Unconfirmed media reports claimed that unidentified helicopters have been spotted over the city, two days after rebel aircraft were used in a military coup attempt to attack police and government buildings in Ankara.